Couldn't you still recover from amanda tapes if the data where
written in 'chunksize' bits across more than a single tape ?

I mean, keep the chunks in order so you can find them, append them
together when writing the tape to limit the amount of reassembly
work. How are chunks re-assembled by taper now ?

Couldn't we recover with "# dd" and "# cat >>" or would reassemble
need to be more complex than that ?

> On Thu, May 15, 2003 at 09:43:24AM +0200, Paul Bijnens wrote:
> > 
> > Maybe a refinement to taperalgo (extra option?) .
> > What should taperalgo decide when e.g.the tape is 50% full, here are no
> > files ready on holdingdisk that fit on the current tape, but there are
> > still DLE's to be dumped some of which will fit.
> > Should it wait for those DLE's (wasting time), should it skip to the
> > next tape (wasting tape)?  Or should it try the smallest one, and hope
> > it will fit (saving tape and time) or risk to run into end of tape
> > (wasting lots of time), or...
> 
> You certainly raise good issues here Paul.
> Ones I had not considered.
> 
> 
> > The situation would be much better if (maybe only some) DLE's would
> > be split across tapes, like suggested in a mail recently by Brian Cutler.
> > In this case you would only lose the last chunk that has to repeated
> > on the next tape.  This lets you control your wasted tape and time,
> > by tuning your chunksize.
> 
> Letting a DLE split across multiple tapes (no need to limit it to 2)
> has long been a desired feature in amanda.  I suspect that some potential
> users have chosen other software specifically because amanda lacked the
> ability to use multiple tapes for a single DLE.  It would certainly
> address the situation we are currently discussing.
> 
> I wonder if taperalgo would still be a needed/useful/needed feature if
> writing DLE's to tape in chunks were implemented.
> 
> Implementing the ability to split a DLE across multiple tapes would
> continue a trend away from a feature of amanda that attracted me;
> the ability to recover a dump using standard, non-amanda tools.
> The RAIT driver was the first salvo to degrade this feature.
> 
> 
> > You could get even more complicated if you have two tape drives, and
> > let amanda fill the two drives at the same time, planning which DLE
> > goes on which tape to optimize the space and time.
> 
> Ohh, now that sounds like fun.  You might also wish to anticipate later
> completing DLE's based on their estimates.  But that would probably
> involve too much linkage between the front and backends of an amdump.
> 
> 
> -- 
> Jon H. LaBadie                  jon AT jgcomp DOT com
>  JG Computing
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